Protecting molten magnesium



Patented Jan.- 31, 1928,

.U'NlTE-D sTA1. ES"

inseam mus, NEW YORK, ,assrenoa 'ro AMERICAN mom H, osnomvn, on

MAGNESIUM CORPORAIKI'H, OF NIAGARA FALLS, NEW YORK, ACORPOBATION OF imwYORK.

Jlo Drawing.

8 above its melting point, 651 de s 0.,wi1l

combine with both oxygen an nitrogen of the air. .-In melting andcasting magnesium and high magnesium alloys,it is necessary to vide somemeans to protect the -metal m l I 10 grom burning, otherwise the castmetal will have magnesium compounds occluded in it;

which cause'defects and weaknesses ill/the castings. -In fact, failure,to rotect the metal. from burningmay result in the complete consumptionof the magnesium before.

it can be-cast; g For attaining the. desired end, I have discovered thatif a small quantity of glycerine, preferably anhydrous, is brought intocontact with the molten metal in a closed receptacle, that burning ofthe magnesium is obviated and that no deleterious products areformed;resultingfrom decompositlon of the lycerine so that-the finishedcastings are free from imperfections with a consequent improvement intheir physical pro 8113165 The lycerine maybe added at t e beginning othe melt and it may be added from time to time as the melting proceeds.In practice, however, there is a covei on the pot and while it is notgas-tight, it might be called circulation tight, that is to say, Itprevents the ready escape of the vapors which may be formed by thebreakmg down of the liquid or vaporized lycerlne.

In starting a melt, the c arge of magnesium containing metal having beenplaced in the furnace, a few cubic centimeters of as nearlyanhydrous'glycerine as posslble are added, all openings are covered withrather close fitting covers, and the heat is turned.

on. During the pouring or tapping, and whenever it is necessary toexpose the interior of the pot to the open air, a few additional dropsof glycerine are added so as to always keep the pot filled withglycerine vapor and to exclude the air.

The theory upon which glycerine acts to v prevent oxidation of themolten metal in a follows:

Glycerine boils at approximately 290 declosed receptacle may beexplained in part as grees C. while magnesium melts at 651 dernornc'rmev uom'nn maermsm'm.

Applicatlon fllcd october a7, 1922; Serial No. 597,880.

grees C. Accordingly, when the metal is molten, the glycerine or productthereof will be n the form ofa vapor and is effective because itexcludes the air and at the same time, it does notvquickly react withthe molten' magnesium. .The specific gravity of the vapor of glycerineat the melting point of the metal 1s comparatively high and for thatreason it does not escape easily from a fairly well closed up vessel.tity of glycerine is brought into contact with the: molten metal, thevolume of the vapor is many times the volume of the initial liquidmaterial. Theglycerine vapor originates in the lower portion of the gasspace which is over the metal and the tendency accordingly is togradually but continuously forceout sium does not undergo anyappreciable loss.

Ths is probably the condition during the early stages of melting whenthe temperature is still fairly low. As the temperature rises, theglycerine vapor begins to form.

other compounds which also afford protection to the molten metal but notcombining with it. Ultimately there is, of course, a completedecomposition of the glycerine or at least an escape of it from the potwhich is the practical reason why a small quantity is intermittentlyadded during the melting operation. As the temperature of the metalapproaches its melting point, glycerine bemg an organic substance isfairly easily changed into other compounds when its vapor is brought tosuch an elevated temperature. The strong reducing action of themagnesium probably promotes the decompos1 ion.

When a small quan-' Glycerine is a trihydric alcohol having the englycerine va- "of molten magnesium or its alloys as would otherwise befreely exposed to. the air, such as surfaces in the melting crucible orpouring stream; and as the continuation of this stream surface, thesurfaces of the. molten metal in the openings of the-mold where it isfreely exposed to the air. 0

I claim:

1. The method of protecting molten magnesium and magneslum alloyscomprising bringing in contact with the molten metal,

products resulting from-the heating of glycerine above the melting pointof said metal.

2. The method of protecting molten magnesium and magnesium alloyscomprising treating the molten metal in .a closed receptacle from timeto time with a relatively small quantity of glycerine.

3. The method of protecting molten magnesium comprising treating themolten magnesium in a closed receptacle with a rela:

tively small quantity of glycerine and providing a vent in the saidreceptacle to permit escape of the displaced gases.

4. A method of protecting molten maging during melting and pouring,comprising bringing in contact with the surface of the metal in a closedreceptacle, :1 material having a boiling point which is relatively highbut lower than the melting point of the metal, the said material in agaseous condition serving to prevent burnin of the metal, without itselfreacting excessively with the molten metal, the specific gravity of thesaid material in a gaseous condition bein relatively highfiwhereby itdoes not rea 11y escape from the closed receptacle.

4 6. Method of protecting molten magnesium and magnesium alloys againstburning at surfaces freely exposed to the air, comprising bringing incontact with such surface of the molten metal a material having aboiling point between about 290 C. and

650 C., which will react only slowly with the molten metal and whichwill produce a vapor heavier than air.

In testimony whereof I afiix my signature.

HAROLD H. OSBORNE.

